It is well known that during the building of pneumatic tires, a plurality of tire components, such as stabilizer plies and treads, for example, are laid upon a tire building drum for the formation of a "green" or uncured tire. It has further been found and is well know that tire performance, wear, and other features are directly dependent upon the accuracy with which the tire is "built." In other words, the alignment of the tire components with respect to each other and with respect to the center line of the tire itself is paramount in assuring a tire which performs and wears properly.
Since tire building is, to a large extent, performed manually, human error is to be expected. Often times the tire components walk or "snake" about the tire building drum, deviating from the desired lateral position relative to the tire building machine. These deviations may come about due to some error in judgment of the operator, or may gradually appear in the operator's work effort over a course of time. In additional, machine misalignment, machine control errors, or material variations may occur and, because of the gradual nature of the evolvement of such errors, not be detected.
Of particular interest to the invention herein is an apparatus and technique which allows for the monitoring of the lateral edges of the components of a tire as it is being built upon a drum and to render an indication of the alignment of those components with each other and with the center line of the tire immediately after the placement of the components upon the drum. Previously, it has been known from Japanese Patent Application No. 1-332546, entitled "Apparatus For Detecting Edge Positions Of Material," to employ a pair of cameras above a drum receiving components of material thereon and to sense and/or monitor the positions of the lateral edges of the components thereby. This art particularly teaches that the component edges can be made apparent by means of illuminating the edges in such a manner as to cast a shadow, with the cameras monitoring the position of the shadow rather than the position of the component edges themselves. Such is given to inherent inaccuracies and difficulties in calibration. Since the two edges are viewed by separate cameras, correlating the images between the two cameras is required, but is difficult to implement. Further, should the thicknesses of the components vary, the shadows cast thereby will not be predictably indicative of the position of the edge itself.
Accordingly, there is a need in the art for an apparatus and technique for monitoring the component edges in a tire building process which is absent the shortcomings of the prior art.